Instituto de Química, Universidade Federal do Rio Grande do Sul, 91501-970, Porto Alegre, RS, Brazil.
Instituto de Química, Universidade Federal do Rio Grande do Sul, 91501-970, Porto Alegre, RS, Brazil; Instituto Nacional de Ciência e Tecnologia do CNPq - INCT de Energia e Ambiente, Universidade Federal da Bahia, 40170-115, Salvador, BA, Brazil.
Talanta. 2022 Feb 1;238(Pt 1):122998. doi: 10.1016/j.talanta.2021.122998. Epub 2021 Oct 29.
In this work, a method for total sulphur determination in automotive gasoline using dried matrix spot sampling is proposed. The method is based on the deposition of the sample on a cellulose-based filter paper and subsequent sulphur quantification via CS diatomic molecule using high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS). The sample deposition was carried out, along with the chemical modifier, on a 20-mm filter paper disc previously adapted into a polytetrafluoroethylene (PTFE) mould. The liquid phase was removed by heating the PTFE mould, and then the gasoline sample-embedded filter paper was punched in smaller discs (procedure A) or pulverised (procedure B) before the analyses. The mixture of Pd and Mg was used as chemical modifier to stabilise the sulphur compounds on the filter paper and on the graphite furnace. All the calibration curves constructed using seven different sulphur-containing compounds had a coefficient of determination higher than 0.995 and a linear range from 2 to 150 mg kg S. By using the optimised conditions, the best characteristic mass, limits of detection and quantitation were 6 ng, 0.6 and 1.8 mg kg, respectively. The two sampling procedures (A and B) were evaluated for real samples, and procedure B was chosen since it markedly improved the precision. Using this procedure, satisfactory recovery values from 95 to 106% were obtained in the spike-recovery tests. In addition, the S concentrations for the certified reference materials were not statistically different from the certified values at 95% confidence level. Sulphur concentrations from 20 to 46 mg kg were found in the six analysed gasoline samples, and these values were statistically assessed using a reference method (ASTM 5453). Spectral interference caused by MgF and MgCl diatomic molecules was observed and investigated.
本工作提出了一种采用干基质点采样测定车用汽油中总硫的方法。该方法基于将样品沉积在纤维素滤纸上，然后通过高分辨率连续光源石墨炉分子吸收光谱法（HR-CS GF MAS）用 CS 双原子分子定量测定硫。样品沉积与化学改性剂一起在先前适应于聚四氟乙烯（PTFE）模具的 20mm 滤纸圆片上进行。通过加热 PTFE 模具除去液相，然后在分析之前将嵌入汽油样品的滤纸打孔成较小的圆片（程序 A）或粉碎（程序 B）。Pd 和 Mg 的混合物被用作化学改性剂，以稳定滤纸和石墨炉上的硫化合物。使用七种不同含硫化合物构建的所有校准曲线的相关系数均高于 0.995，线性范围为 2 至 150mgkgS。通过使用优化条件，最佳特征质量、检测限和定量限分别为 6ng、0.6 和 1.8mgkg。对实际样品评估了两种采样程序（A 和 B），选择了程序 B，因为它显著提高了精密度。使用该程序，在加标回收测试中获得了 95%至 106%的满意回收率。此外，在 95%置信水平下，对于认证参考材料的 S 浓度与认证值没有统计学差异。在六个分析的汽油样品中发现了 20 至 46mgkg 的硫浓度，这些值使用参考方法（ASTM 5453）进行了统计学评估。观察到并研究了 MgF 和 MgCl 双原子分子引起的光谱干扰。
